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The mammalian circadian clock lying in the suprachiasmatic nucleus (SCN) controls daily rhythms and synchronizes the organism to its environment. In all organisms studied, circadian timekeeping is cell-autonomous, and rhythmicity is thought to be generated by a feedback loop involving clock proteins that inhibit transcription of their own genes. In the(More)
Increases in arousal and activity in anticipation of a meal, termed "food anticipatory activity" (FAA), depend on circadian food-entrainable oscillators (FEOs), whose locations and output signals have long been sought. It is known that ghrelin is secreted in anticipation of a regularly scheduled mealtime. We show here that ghrelin administration increases(More)
Calbindin-D(28K)-immunoreactive cells are tightly packed within a discrete region of the caudal aspect of the suprachiasmatic nuclei of hamsters. These cells receive direct retinal input and are Fos-positive in response to a light pulse. Knowledge of their afferent and efferent connections is necessary to understand suprachiasmatic nucleus organization. The(More)
Although the suprachiasmatic nuclei (SCN) have been intensively analyzed, they contain a population of cells that has not yet been characterized. In this study, we examined the distribution of cells immunoreactive (ir) for calbindin-D28K (CaBP), calretinin (CR), parvalbumin, vasopressin-associated neurophysin (NP), substance P (SP), vasoactive intestinal(More)
We studied the dependence of the expression of protein kinase C immunoreactivity (PKC-IR) in the rat retina on the light:dark (LD) cycle and on circadian rhythmicity in complete darkness (DD). Two anti-PKC alpha antibodies were employed: One, which we call PKCalphabeta recognized the hinge region; the other, here termed PKCalpha, recognized the regulatory(More)
The suprachiasmatic nucleus (SCN) of the hypothalamus regulates daily rhythms in physiology and behavior. It is composed of a heterogeneous population of cells that together form the circuits underlying its master clock function. Numerous studies suggest the existence of two regions that have been termed core and shell. At a gross level, differences between(More)
The suprachiasmatic nucleus (SCN) is the locus of a hypothalamic circadian clock that synchronizes physiological and behavioral responses to the daily light-dark cycle. The nucleus is composed of functionally and peptidergically diverse populations of cells for which distinct electrochemical properties are largely unstudied. SCN neurons containing(More)
The suprachiasmatic nucleus (SCN) of the hypothalamus is the neural locus of the circadian clock. To explore the organization of the SCN, two strains of transgenic mice, each bearing a jellyfish green fluorescent protein (GFP) reporter, were used. In one, GFP was driven by the promoter region of the mouse Period1 gene (mPer1) (Per1::GFP mouse), whereas in(More)
The bilaterally symmetrical suprachiasmatic nuclei (SCN) of the hypothalamus are the loci of the mammalian clock controlling circadian rhythms. Previous studies suggested that all regions of the SCN are equipotential as circadian rhythmicity is sustained after partial ablation, as long as approximately 25% of the nuclei are spared. In contrast to these(More)
We investigated parvalbumin immunoreactivity (PA-IR) in the retinas of rats maintained on a 12:12 h light:dark cycle, or after being placed in constant darkness for 24–72 h. Retinas were harvested at zeitgeber and circadian times 02:00, 06:00, 10:00, 14:00, 18:00 and 22:00 h. PA-IR was found primarily in retinal amacrine cells of the AII subtype. In a(More)